We know that people have gotten fatter over the course of the last 60 years. We don't yet know exactly why, writes David Berreby in a fascinating long read at Aeon Magazine. Yes, we know that diet and exercise have something to do with it — but they don't explain all the changes we've seen. Yes, you can find plenty of people who will proselytize to you about how they've found the One True Obesogen — but in order to do that they have to ignore contradictory studies and studies that suggest there's more than one thing going on.

Long story short, if we know anything about obesity its that it's complicated — and that's true for both the factors that create an obesity epidemic, and the factors that allow people to reliably and permanently lose weight. The problem, writes Berreby, is that legislation on the subject has been focused pretty much entirely on diet and exercise, alone. That suggests that laziness and gluttony are the primary reasons people get fat. But we don't know that that's true.

Berreby's piece is a really fun read, mainly because it can serve as an introduction to the plethora of far-reaching and often contradictory data on obesity. There are lots and lots and lots of different things that might be behind the obesity epidemic, from industrial chemicals, to sugary high-fat diets, to epigenetic factors that pass the environmental impacts of one generation on to their descendants. There are even social factors that influence how exposed you are to other risks and affect your ability to make the healthy choices when it comes to diet and exercise. His point: If we want to tackle this as a society, then our legislative response shouldn't begin and end with programs that punish people for being fat, reward them for losing weight, or limit portion sizes at restaurants. We also need to try out programs that put some of the other legitimate ideas to the test.